Abstract

The Ashkenazim are a well‐studied population with a dynamic and unique history. The spread of Jewish populations from the
Middle East to locations in the Diaspora in the past 2000 years represents a microcosm of the evolutionary processes affecting
modern humans as they dispersed out of Africa (e.g. founder effects, migrations, admixture and adaptation). Ashkenazim – Jews
who trace their ancestry to founders who moved to the Rhine Valley in the fourth century – are no exception. Recent studies
both support and refute long‐standing hypotheses of Ashkenazi origins. Together, the results Strengthen the inferences that
Ashkenazi Jews trace their ancestry to a genetically diverse population in the Middle East that underwent a series of founder
events – reducing genetic diversity relative to the ancestral population – and that subsequently experienced significant gene
flow during the period of Ashkenazi residency in Europe.

Key Concepts

Ashkenazi Jews are genetically more similar to each other than to individuals from other populations.

Ashkenazi Jews are most closely related to other Jewish populations.

The Ashkenazim likely arose from a genetically diverse population in the Middle East.

Ashkenazi Jews appear equally close to both Middle Eastern and European populations.

Ashkenazi Jews are not closely related to modern populations that best represent the Khazars.

Figure 1. Four possible models of AJ origins. Model (a) depicts a complete Middle Eastern origin with no gene flow from Europeans, with
multiple population reductions and expansions. Model (b) depicts a partial Middle Eastern origin with gene flow from Europeans,
and multiple population reductions and expansions. Model (c) model depicts a complete European or Turkic origin, with no ancestry
from the Middle East. The time points a, b and c indicate the Out of Middle East (100–80 generations ago), out of Rome (70–50
generations ago) and eastern expansion (40–20 generations ago) events, respectively.

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